Process of obtaining substantially pure hydrogen



G. clcALl 1,807,897 PROCESS 0F OBTAINING SUBSTANTI'ALLY PURE HYDROG'EN June 2, 1931.

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Patented June 2, 1931 UNITED STA-TES GIOVANNI CIQCALI, OF BOLOGNA, ITAIiY PROCESS OF OBTAINING SUBSTANTIALLVY PURE HYDROG- EN Application led Iune 19, 1.925, Serial No. 38,385, and in Italy :February 16, 1925.

Water gas (or the like), previously freed from sulphur and carbon dioxide and other gases that can be readily eliminated by the ordinary methods, is reduced to contain only hydrogen and carbon monoxide. The gaseous residuey of this preliminary purification, viz. the Whole of the hydrogen and carbon monoxide contained in the water gas, before treatment in the apparatus illustrated in Figs. 1-2-3, must be subjected to a preliminary treatment which may be carried 'out by any physical or lchemical process preferred, in order to remove a portion of the carbon monoxide content. Referring to the drawings, Fig. 1 is a diagrammatic view, partly in section, of a system of apparatus suitable for carryingout the process of this invention, and Figs. 2 and 3 are diagrammatic views showing modified arrangement of compressors and coolers for use in the apparatus system illustrated in Fig. 1. After the preliminary treatment just referred to, the resulting mixture consisting of approximately the whole of the original. hydrogen content of the water gas and a small amount of carbon monoxide,

which is far less than was originally contained in the water gas, is conveyed by pipe 1 (Fig. l) through the cock R controlling its iiow and is mingled with such a weight of nitrogen supplied by pipe 2 throughcock R1 that the percentage of nitrogen plus carbon monoxide referred to the hydrogen present in the resulting mixture is equal 'to the percentage of the water gas carbon monoxide re- 3? ferred to the hydrogen present in the original water gas. That is, the nitrogen added equals the amount of carbon monoxide removed by preliminary purification.

40 The' resulting mixture is compressed up to a certain pressure in the internally watercooled compressor C. After leaving the compressor C the mixture undergoes a further cooling in the heat-exchange apparatus or refrigerator -/r. The said arrangement might alsobe replaced (Fi 2 and 3) by two compressors C1 and C2; 1 compressing the nitrogen and C2 compressing the gaseous mixture as defined above resulting from n the partial purification of the water gas, a

5 single external refrigerator -fras per Fig.

2 or two external refrigerators -1'1- and rras per Fig. 3, being provided. n

F-rom the refrigerator fr- (Fig. 1), or from the refrigerator 7'- (Fig. 2), or from the two refrigerators r1- and -4'2- (Fig. 55 3), the mixture is led to the middle pipe of the three-pipe coil or heat-exchange device S. At the outside of this middle pipe Hows in opposite direction, as will be seen later, the purified hydrogen (in the outer pipe) and, in the inner coil pipe, Ypiow the nitrogen and carbon monoxide that have been separated fromthe hydrogen and are very cold; the mixture is therefore cooled. The mixture issuing from S is delivered through B' 65 l into the column Q.

Here the mixture rising up-thr'ough the pans P is bubbled through-the liquid nitrogen with which the pans are filled. The

Vmore readily lqueiiable component, viz. the

carbon monoxide, tends to liquefy in greater proportions than the other components; simultaneously the pans, working as rectifiers, will let the morevolatile gas, viz. the hydrogen, disengage itself in greater proportions. The carbon monoxide on liquefying will cause a portion of the nitrogen to volatilize, nitrogen being more volatile than carbon monoxide. The hydrogen, nitrogen and slight traces of carbon monoxide will move upward and enter the pipes T, where the greaterportion of the nitrogen and the whole of the carbon monoxide, owing to the extremely low temperature, will condense and drop back into the pans P, while the hydrogen will become less rich in carbon monoxide as it gets nearer to the upper end of the column. The hydrogen that reaches the column top, freed of carbon monoxide but still containing traces of nitrogen, is conveyed through the outlet K to the expander -ewhere, in consequence of the e anding work, its temperature is lowered. A er expansion, the hydrogen returns through E into the `col umn Q where it cools the gases flowing up throng the tubes T ofthe column Q, and goes to the column outlet F, whence it is led by a pipe 3 into the outer pipe of the coil S, there to further eool the mixture supplied by the compressor r by the comlo -tank W, where they evaporate and cool the gas iowing inside of the pipes T.

The nitrogen and carbon monoxide vapours leavin the column through the outled by the pipe 4 into the inner pipe of the heat exchange device S, where they cool the gas mixture iiowing in opposite direction through the middle pipe, as

. already stated.

Should a single purification not suilice to supply hydrogen showing `the degree of purity required or the uses for which the hydrogen is intended, the operation'may be repeated inpone or more further sets of apparatus identical' to those described (Figs.

1-2-3), further nitrogen being added to the` mixture in order to replace the carbon monoxide that has been removed by the previous operations, so that the proportion stated a ove be always preserved. G

Having now particularly described and ascertained the nature of my said invention and in what manner the same is to be performed, I declare that what I claim is 1. The process of recovering hydrogen practically free fromV carbon monoxide and containing only traces of other gases from a mixture containing hydrogen and carbon monoxide such, as water gas or the like, comprising removinga substantial portion of the carbon monoxide from the mixture by preliminary purication, diluting said partially lpurlied mixture with a gas which lipueiies at a higher temperature than that o hydrogen and ower temperature than that of carbon monoxide, the amount of said diluent gas being meterially greater than the amount vof carbon monoxide remaining after materially greater than the amount of carbon monoxide remaining after theI prelimi- 'nary puricationcompressing and cooling said diluted mixture, and separating the hydrogen from -said compressed mixture by fractionally condensing the carbon monoxide and nitrogen therefrom.

3. The roce` as in claim 1 in which the amount ofpdiluent gas added is several times greater than the amount of carbon monoxide remaining after the preliminary purification. 4. The'process as in claim 2 in which the amount of nitrogen added is several times greater than the amount of carbon monoxide remaining after the preliminary purification.

5. The processas in claim 2 in which the amountlof nitrogen added is substantially equal to the amount of carbon monoxide removed by the prelimina purification.

6. The process of obtaimng hydrogen practically free from carbon monoxide although containing traces of nitrogen from gaseous mixtures containing hydrogen and carbon monoxide, such as water gas, comprising removing the greater part of the carbon monoxide from said gaseous mixture by preliminary puriication adding gaseous Introgen to the partially .puried gaseous mixture, the amount of nitrogen being suicient, when liquefied, to` wash out the carbon monoxide from said mixture, subjecting the nitrogenous mixture to comparatively high pressure and cooling the compressed mixture without expansion thereof to produce -a liquefaction of, the nitrogen and carbon monoxide con- 100 stituents of said nitrogenous mixture, and separating the gaseous hydrogen from the 1i ueed nitrogen and car on monoxide.

The rocess as in claim l6 in which the cooling o the compressed mixture is produced by expansion with performance of work of the resultant carbon 'monoxide-free hydrogen.

, GIOVANNI CICALI.

the preliminary purification, compressing and cooling said. diluted mixturefand separating the hydro n from said cooled mixture by :Eractiona y .condensing the carbon monoxide and diluent therefrom while in said compressed con tion.

2. Ihe process .of recovering hydrogen practically free lfrom carbon monoxide and containing only tracer of nitrogen from a mixture containing hydrogen and carbon monoxide such as water gasorthe like comprising removing a substantial portion of the c arbon monoxide from the/ mixture by preliminary-purification, diluting said partially purified mixture with an amount of nitrogen 

